Tuning system for pianos



Feb. 26, 1935. E. GROVEN 1,992,571

TUNING SYSTEM FOR PIANOS Filed March 22, 1934 Patented Feb. 26, 1935 PATENT OFFICE TUNING SYSTEM FOR PIANOS Eivind Groven, Ekeberg Haveby, near Oslo, Norway Application March 22, In Germany "6 Claims.

The present invention relates to pianos and provides a piano which maybe completely retuned during play by the manipulation .of a key. In order toachieve this purpose equally .denominated strings of all octaves are associated with common tightening means, and various combinatlons of these tightening means are adapted to be actuated by means of a particular key.

It is known'to retune stringed instruments by means of adjustable tightening means, the several strings being connected to one arm of a twoarmed lever, the other arm of which is connected withthe tightening means. The arrangement in accordance with the present invention differs from the known retuning devices therein that a number of complete retunings of the piano may be effected by the manipulation of separate keys, and the invention is mainly based on .the fact that a pure tuning of a piano can only be obtained by completely retuning the whole piano when passing from one musical key to another.

Further, in accordance with the present 'invention it. is possible to play not only in the musical keys at present used on thepiano, butalso in a number of new musical keys.

The theoretical basis for the invention is given below:

It is known that the several strings formingone octave of a string instrument such as a piano, may be so tuned with relation to each other that the ratio between the natural frequencies of the several strings may be given as fractions of whole numbers, whereby the conditions for obtaining harmonic combinations of tunes are satisfied in the best possible manner.

In accordance with this principle it is feasible to determine the ratio between all twelve fre-. quencies forming an octave on the basis of the major triad with a frequency ratio of 4:5:6.

Under these conditions the frequency ratio for A tuning in accordance "with this frequency ratio only partly satisfies the conditions of harmonic soundefiect for a few major keys, and more orless dissonant combinations are obtained for all other keys, which means that for these keys the frequency ratios between the tones of the triad can no longer be expressed by low whole numbers.- The condition whereby pure sound effects can be obtained in all interval combinations necessary in modern music can therefore not :be satisfied by a fixed tuning of the strings, and for that purpose therehas been suggested the equal temperament tuning developed by J. S.

will be:

1934, Serial No. 716,877 May 21, 1931 Bach, in accordance with which the frequencies of two adjacent strings have a fixed ratio over the entire piano, said ratio being expressed for all tones of the scale, except for the octaves, by means of irrational numbers.

It is true that the difference from the ideal pure tuning of the equal temperament tuning in most cases is not very big, and it may be said that the equal temperament tuning gives the most satisfactory compromise when fixed tuning is to be used. Nevertheless there will always be an error present in all combinations of tones, and this error in some cases may be considerable. I In accordance with my invention the strings of the instrument are provided with tightening means, by means of which the tightening of the strings may be instantly changed, said tightening means being preferably adapted to adjust the tightening of each string or set of strings for at least three frequencies, whereby the conditions of pure tuning for all musical keys utilized at present may be satisfied.

Under certain conditions it may be desired to be able to adjust each string for five different frequencies, whereby it is made possible to reproduce certain kinds of music which cannot be reproduced exactly on the pianos at present in use.

By means of the arrangement in accordance with the present invention it is obtained that a pure tuning of the instrument may be attained for all musical keys at present in use and for all chords utilized in the usual musical keys which are based on the combination of quarter tones etc. i

In accordance with a practical embodiment o the invention the strings at one end are preferably associated with tightening means, which are actuated by means of electric or pneumatic adjusted devices adapted to be operated by means of keys forming a separate key board in front of the ordinary key board. By actuating a particular key of the retuning key board a certain number of tightening devices are put in operation, where by the complete instrument is retuned for a new musical key.

The number of tightening devices for the strings and the number of retuning keys to be used will depend on the degree of purity re quired. For a stringed instrument which is to satisfy all conditions for pure tuning in all cases it is necessary to use on the whole 23 different retunings, which may be obtained by means of a retuning key board having 23 keys, each key actuating one particular combination of tightening devices.

On the drawing is diagrammatically illustrated how the retuning of a string set for four difierent frequencies may be obtained electrically by means of four different retuning keys.

The string set 1 at one end is secured to the frame at 2 in the ordinary manner, and at the other end is connected with the short arm 3 of a two-armed lever, which is pivotally connected with the frame at 4. The long arm 5 of said lever is connected by means of link 6 with the rotatable core 7 of a rotatable magneto.

Said core 7 is provided with a radial arm 8 carrying an arc-shaped contact strip 9, 10. The two parts 9, 10 of said strip are separated from each other by means of a connecting piece 11 of insulating material.

Above the contact strip 9, 10 there are placed four coils 12, 13, 14, 15, which are provided with cores 16, 17, 18, 19 suspended in springs and which are pressed against the are 9, 10 when the cores 12, 13, 14, are energized, and comprising four solenoids.

Further there is located above the strip 9, 10 a solenoid consisiting of a coil 20, the core 21 of which acts as a brake on the strip, being pressed by means of a spring against the said strip and being so controlled that the braking action is cut out when the coil is energized. For actuating the whole device there is provided a source of current 22, to which all coils are connected in parallel by means of leads 23, 24, 25, 26. In these leads the retuning keys 27, 28, 29, are connected, so that the currents may be closed by depressing said keys.

Further, the movable cores Iii-19 are connected with the leads 2326.

From the source of current 22 a lead 31 goes to the stator coils 32, 33 of the rotating magneto and is connected with the middle point 34 of the rotor coil 35 thereof. The two ends of said rotor coil are connected through leads 36, 37 with the sections 10, 9 of the contact strip.

By depression of a key, for instance key 30, the corresponding coil 15 will be energized, so that the core 19 thereof is brought into engagement with the strip.

Thereby a self -closing circuit is closed through leads 31, 36, strip 10 and core 19 for coil 15. Further, coil 20 is energized, so that the brake 21 is lifted and the strip 9, 10 is permitted to move. Further, the rotating magneto is energized through lead 31, stator coils 32, 33, lower part of rotor coil 35, lead 36, strip 10, core 19, coil 15 and lead 38, whereby the contact strip is rotated clockwise until the insulating member 11 arrives under core 19, whereby all currents are interrupted and the strip is stopped by means of brake 21.

As the self-closing circuit is established as soon as the core 16-19 arrives in engagement with the contact strip, a very short depression of the retuning keys 27-30 is required.

Simultaneously with the retuning of the string set I obviously the corresponding retuning of the corresponding string set in all other octaves is effected, as the depression of a particular retuning key will actuate the rotating magnets for the tightening of strings belonging to the other octaves.

For each core 16-19 but must acordingly be provided a number of coils corresponding to the number of retunings which are to be effected.

What is claimed is:

1. A tuning device for stringed instruments of several octaves range, comprising a tightening means common to strings of equal denomination of all the octaves to be tuned, means for actuating said tightening means, and a plurality of separate keys, each cooperating with and selectively bringing said last-mentioned means into operation, each to a predetermined and different extent, and each key governing the degree of actuation of the said last-mentioned means, for controlling the amount of tightening, to permit complete retuning in a predetermined manner by the actuation of a single key.

2. A tuning device for stringed instruments of several octaves range, comprising a two-armed lever serving as a tightening means and to one end of which are connected the strings of equal denomination of all the octaves to be tuned,

means for actuating the lever and to which the other end of the lever is connected, and a plurality of separate keys, each cooperating with and selectively bringing said last-mentioned means into operation, each to a predetermined and different extent, and each key governing the degree of actuation of the said last-mentioned means, for controlling the amount of tightening, to permit complete retuning in a predetermined manner by the actuation of a single key.

3. A tuning device for stringed instruments of several octaves range, comprising a two-armed lever serving as a tightening means and to one end of which are connected the strings of equal denomination of all the octaves to be tuned, a rotatable magneto to the core of which the other end of said lever is connected, a plurality of solenoids, a source of current, an arc-shaped contact strip insulated into two conductive portions and cooperating with said solenoids and each said conducting portion being connected in circuit with the stator and rotor coils of said magneto and with said source of supply, the said contact strip being connected to and rotated with said magneto, the said solenoids being paralleled off said source of current, and kays controlling the circuit of each solenoid, closing of the circuit of a particular solenoid causing the movement of the magneto rotor and the arc-shaped contact strip through a predetermined distance, and the consequent predetermined movement of the tightening lever.

4. A tuning device for stringed instruments of several octaves range, comprising a two-armed lever serving as a tightening means and to one end of which are connected the strings of equal denomination of all the octaves to be tuned, a rotatable magneto to the core of which the other end of said lever is connected, a plurality of solenoids, a source of current, an arc-shaped contact strip insulated into two conductive portions and cooperating with said solenoids and each said conducting portion being connected in circuit with the stator and rotor coils of said magneto and with said source of supply, the said contact strip being connected to and rotated with said magneto, the said solenoids being paralleled oil said source of current, keys controlling the circuit of each solenoid, closing of the circuit of a particular solenoid causing the movement of the magneto rotor and the arc-shaped contact strip through a predetermined distance, and the consequent predetermined movement of the tightening lever, and an additional solenoid serving as a brake for the contact strip and magneto, and adapted to be disengaged from said contact strip upon energization of its coil, its coil being connected in series with the coil of each of the first-mentioned solenoids.

5. A tuning device for stringed instruments of several octaves range, comprising a tightening means common to strings of equal denomination of all the octaves to be tuned, means for actuating said tightening means through selected predetermined amounts, a self-closing circuit energizing and controlling said actuating means, a plurality of means for starting said self-closing circuit into operation for a predetermined interval, each interval being different from each other and each corresponding to one of said selected predetermined amounts through which said tightening means are actuated, and a separate key for each of said plurality of means, for bringing the same into operation at will.

6. A tuning device for stringed instruments of several octaves range, comprising a tightening means common to strings of equal denomination of all the octaves to be tuned, means for actuating said tightening means through selected predetermined amounts, a circuit energizing and controlling said actuating means, a plurality of means for controlling said circuit, each key being adapted to cause the circuit to cooperate with and selectively bring the actuating means into operation, the extent of operation being predetermined and difierent for each key, each key governing, through the circuit, the degree of actuation of the actuating means, thereby controlling the amount of tightening of the springs, to permit complete retuning of the said strings of equal denomination of all the octaves to be tuned, in a predetermined manner by the actuation of a single key.

EIVIND GROVEN. 

